C. jejuni is a bacterium commonly associated with poultry, since it naturally colonises the digestive tract of many bird species. Contaminated drinking water and unpasteurized milk provide an efficient means for distribution in human populations. Contaminated food is a major source of isolated C. jejuni infections, with incorrectly prepared meat and poultry normally being the source of the bacteria.
Infection with C. jejuni usually results in enteritis, which is characterised by abdominal pain, diarrhea, fever, and malaise. The symptoms usually persist for between 24 hours and a week, but may be longer. Diarrhea can vary in severity from loose stools to bloody stools. The disease is usually self-limiting. However, it does respond to antibiotics. Severe (accompanying fevers, blood in stools) or prolonged cases may require ciprofloxacin, erythromycin, azithromycin or norfloxacin. The drug of choice is usually erythromycin. About 90% of cases respond to ciprofloxacin treatment. Fluid and electrolyte replacement may be required for serious cases.
The first full-genome sequence of C. jejuni was performed in 2000 (strain NCTC11168) with a circular chromosome of 1,641,481 base pairs
As mentioned, C. jejuni infections may successfully be treated by administration of antibiotics to patients in need thereof, but that would not prevent acute illness. Further, due to careless or thoughtless use of powerful antibiotics, many pathological germs, including C. jejuni become resistant against antibiotics over time. In particular in hospitals, treatment with antibiotics can prove inadequate: not only will a C. jejuni infection be life-threatening for patients that already suffer from other health problems meaning that treatment with antibiotics may simply be non-effective within the relevant time-span, but in addition antibiotic-resistant C. jejuni strains will also withstand treatment with those antibiotics used as the initial choice in treatment. There is thus a need to provide alternatives to current treatment regimens. Also, infection with C. jejuni is associated with reactive arthritis and Guillain-Barré Syndrome.
Vaccination is considered to be a very effective method of preventing infectious diseases in human and veterinary health care. Vaccination is the administration of immunogenically effective amounts of antigenic material (the vaccine) to produce immunity to a disease/disease-causing pathogenic agent. Vaccines have contributed to the eradication of smallpox, the near eradication of polio, and the control of a variety of diseases, including rubella, measles, mumps, chickenpox, typhoid fever.
Before “the genomic era”, vaccines were based on killed or live attenuated, microorganisms, or parts purified from them. Subunit vaccines are considered as a modern upgrade of these types of vaccine, as the subunit vaccines contain one or more protective antigens, which are more or less the weak spot of the pathogen. Hence, in order to develop subunit vaccines, it is critical to identify the proteins, which are important for inducing protection and to eliminate others.
An antigen is said to be protective if it is able to induce protection from subsequent challenge by a disease-causing infectious agent in an appropriate animal model following immunization.
The empirical approach to subunit vaccine development, which includes several steps, begins with pathogen cultivation, followed by purification into components, and then testing of antigens for protection. Apart from being time and labour consuming, this approach has several limitations that can lead to failure. It is not possible to develop vaccines using this approach for microorganisms, which cannot easily be cultured and only allows for the identification of the antigens, which can be obtained in sufficient quantities. The empirical approach has a tendency to focus on the most abundant proteins, which in some cases are not immuno-protective. In other cases, the antigen expressed during in vivo infection is not expressed during in vitro cultivation. Furthermore, antigen discovery by use of the empirical approach demands an extreme amount of proteins in order to discover the protective antigens, which are like finding needles in the haystack. This renders it a very expensive approach, and it limits the vaccine development around diseases, which is caused by pathogens with a large genome or disease areas, which perform badly in a cost-effective perspective.